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Raising fine silver to the surface


#1

I just finished reading all of the posts regarding “depletion
gilding” silver. I might like to start doing this as a routine part
of finishing my pieces.

I do have a concern and hope I can put it into words so my question
can be understood: I have always used Stop-Ox in my fabrication work
and almost never ever have firescale to contend with. One of the
posts I read says that underneath the fine silver layer is firestain
and sterling. Does that mean that when/if the layer of fine silver
finally wears through, the customer who bought the piece will have
the same product they would’ve had if you had just fabricated in a
manner that caused firestain which you never removed before offering
the piece for sale?

Could the layer of fine silver be expected to last almost
indefinitely on a pendant or would it be expected to wear through in
a year or so if the pendant was worn often?

I am trying to balance the advantages of bringing up the fine
silver, with the resulting better look, against the presumed
disadvantage of a piece which might eventually look worse than a
piece that is carefully fabricated under conditions which prevent or
remove firescale. What my question boils down to, I guess, is whether
or not the post was accurate that says that after repeating heating
and pickling you are left with a fine silver layer that has
firestain underneath it? Or is the fine silver layer just covering
sterling (with no firestain on it)?

J. S. (Sue) Ellington
http://www.jsellington.com


#2

I am working a lot with reticulation, and like you, I use gilding on
my sterling silver surfaces. I read that the process was perfected by
Finnish jewelers who worked for Faberge. In order to get a thick
enough and durable enough coating of fine silver, they regulary went
through the anneal/quench/pickle/brush cycle 6 - 10 times. I do the
same.


#3
I just finished reading all of the posts regarding "depletion
gilding" silver. I might like to start doing this as a routine
part of finishing my pieces. 

I do this on pretty much all pieces that are not going to be
oxidized. It keeps solder from darkening before the rest of the
piece, slows down the tarnish process in general, and gives a
beautiful white finish. It can be done to hide firescale, but if
there was no firescale there before you started, there will not be
any afterwards. Firescale is cupric oxide, and the oxide you create
and pickle off to “bring up the fine silver” is cuprous oxide (I
think it is that, not the other way around). Cuprous oxide is pink,
and easy to remove. Cupric is that nasty purplish-gray stuff that
doesn’t pickle off.

I’ve never had the fine silver wear off a piece in any visible way,
with the exception of one time years ago when I used it to disguise
heavy firescale, and buffed a tad too much (after attaching a
titanium component, so I couldn’t do any more heat work), so it
broke through to the firescale layer. Boy, did that look terrible!
Lesson learned.

If you leave the “pickle white” look on the piece (that is, you
don’t polish it after heating and pickling, a look that was very
popular in europe some years ago) you cannot expect that surface to
last long-- any touch will begin to burnish it, and in protected
areas, it tends to get dirty-looking. Other than that, I know of no
down side to the process if you don’t mind the extra time.

Noel


#4

Hi Sue,

Does that mean that when/if the layer of fine silver finally wears
through, the customer who bought the piece will have the same
product they would've had if you had just fabricated in a manner
that caused firestain which you never removed before offering the
piece for sale? 

Yes. The firestain is not removed; it is covered over by the fine
silver.

Could the layer of fine silver be expected to last almost
indefinitely on a pendant or would it be expected to wear through
in a year or so if the pendant was worn often? 

I have found that depletion gilding can last a very long time on a
piece that is not subject to chronic abrasion – like a ring, for
instance. I have never seen firestain resurface on either my pendants
or my pins and some of my pieces have been back and forth for 2-3
years between consignment galleries. That’s not the same as daily
wear, of course, but it’s a pretty good indication of the durability
of the gilded layer of fine metal. In my case, the metal is 14k gold
but I used to depletion-gild sterling silver as well. My guess would
be that the fine silver layer would not be as durable as the fine
gold; but still, I don’t remember ever seeing the firestain resurface
on the silver either.

When depletion gilding, make sure you’ve got a solid surface layer
of fine metal built up. As you’re heating the piece, watch for small
spots that remain gold (or silver) colored when everything around
them has turned black. Those spots are not fully “cooked”. They can
be caused by specks of dirt on the surface of the piece, so a good
cleaning, after pickling, may be in order. Pop the piece in the
ultrasonic or – just as good – clean it with a soft toothbrush,
detergent and a little baking soda.

The piece won’t be completely gilded until the surface heats to an
even black (or sometimes in the case of gold, dirty brown). This
usually means at least three and more often four or five heatings
(pickling thoroughly between each). Another indication of
insufficient gilding is the appearance of even the slightest red cast
on the pickled metal, which will often appear just in one area.

I use a fairly large but neutral-to-reducing flame (not tight and
bright, in other words). I hold the flame at a small distance from
the piece (never with the hottest part of the flame touching the
metal). Then I keep the flame moving over the metal, periodically
fanning away from the metal so I can see if the black layer has built
up. If you keep the flame directly on the metal at all times, you’ll
never see the black, since the oxide displays itself only when the
heat abates.

Hope this helps.
Beth


#5

I am assuming ALL finishing/polishing/texturing/buffing is done
before raising the fine silver?

J. S. (Sue) Ellington
http://www.jsellington.com


#6
The piece won't be completely gilded until the surface heats to an
even black (or sometimes in the case of gold, dirty brown). 

I think this may cause confusion in beginners, at least with silver.
I am not really familiar with this process on gold, but on silver,
some areas may not darken because the soldering and pickling already
done may have depleted the copper. More to the point, as you repeat
the process, there will be less and less discoloration, with solder
being the last to stop turning dark. This is exactly the point-- as
there is less and less copper at the surface, there is nothing to
turn dark in the flame. When heating doesn’t cause the piece to turn
dark, you know you’ve accomplished your goal-- it is all covered
with fine silver.

One more point-- you don’t need to heat the piece to black, and I
don’t recommend it. If you pickle as soon as any discoloration
appears (it may be yellow) it may take more repetitions, but the
oxide will pickle off quickly and easily. If you overheat, you
will get firescale, which may not really pickle off.

Noel


#7

Buffing and polishing would be done after raising the fine silver.
Rather than use a machine or Foredom tool, I polish the fine silver
surface by hand, using various cloths or chamois.


#8
Could the layer of fine silver be expected to last almost
indefinitely on a pendant or would it be expected to wear through
in a year or so if the pendant was worn often? 

I used this sort of finish for years. One of the problems I had was
when a piece has gotten so scratched up or deeply gouged that it
needs to be refinished. In that case, the fine silver needs to be
"brought up" again (not exactly correct technically, but common word
usage) which can cause pits and problems in solder seams.

In the 1980’s, I became friends with Jeffrey Herman, director of the
Society of American Silversmiths. Jeff makes his living doing
repairs—antique dealers and museums all over the country send work
to him. He showed me beautiful pieces that were marred by the
firescale stains that show after years of love and polishing.

At that point, I went back to using Prip’s Flux to prevent
firescale. When I heard about firescale-free sterling, I sought it
out. And that’s the story of how I met Argentium Sterling Silver, and
fell in love.

Cynthia Eid
http://www.cynthiaeid.com


#9

Hi Noel,

One more point-- you don't need to heat the piece to black, and I
don't recommend it. If you pickle as soon as any discoloration
appears (it may be yellow) it may take more repetitions, but the
oxide will pickle off quickly and easily. If you overheat, you
*will* get firescale, which may not really pickle off. 

You’re right about the color differences when depletion gilding
silver. It’s been so long since I’ve done it with silver, that my
memory is faulty. However, heating to black initially does work
very well. The key is to avoid heating beyond black until the metal
turns red.

I don’t know what happens metalurgically when you do that but it
seems on occasion as if the layer of pure metal burns off leaving
just the firestain on the top surface. If that happens, you have to
start the depletion process again. Is that what you meant by “if you
overheat, you will get firescale”?

I ask because you’re going to get firestain regardless of whether
you overheat or not. The difference is that when the metal is
properly depleted, the firestain lies underneath the layer of pure
metal and isn’t visible. When done improperly, with overheating, the
firestain will resurface and become visible again.

There’s another downside to overheating while depletion gilding and
I made the mistake just yesterday. Since depletion gilding is the
very last step you’ll do (with the torch, that is), if you’re not
careful you can unsolder a finding or, in my case, a bezel!

By the way, there’s a wonderful heat patination/patterning technique
I learned years ago in a workshop with Rachelle Thiewes. First you
thoroughly depletion gild a piece of silver till it’s as white as it
can get. Then you selectively abrade through the white “skin” till
you get down to sterling silver. Heat one last time till the bare
sterling is black and DON’T pickle. The result will be a striking
black on white pattern (which can be maintained by using a sealer).
To anyone who tries this, note that you must keep the metal clean
at all times. Even fingerprints will inhibit the process.

Beth


#10

Hi Sue,

I am assuming ALL finishing/polishing/texturing/buffing is done
before raising the fine silver? 

Polishing and texturing – yes. You can buff LIGHTLY after gilding.
And you can use finishing processes that don’t remove metal, like
burnishing and wire brushing. Such processes will actually strengthen
the outer layer by compressing it.

Beth


#11

This thread is interesting to me because I’ve never done it,
although have seen the effect during routine work. Some questions…

How thick is the fine silver layer assuming its done ten times as
mentioned? ie: how much repolishing will it take?

Do you quench in pickle or air cool first?

How does gilding compare in a practical sense to silver-plating? It
seems to me gilding would take maybe half an hour?, whereas plating
about five minutes. Is there a superior finish with the gilding?

I think someone mentioned scrubbing with a brass brush, would that
not discolor the silver? How about a nickel or stainless steel
brush?(which I used in my silversmithing days to good result)

I will look for a suitable chunk of scrap to experiment with, might
be fun. Oh Boy, Saturday night in the shop, better than a blind
date.


#12

I did depletion silvering for the first time yesterday. I had no
idea how to impart shine without removing the silver and couldn’t
find anything in the archives or on an Internet search that I felt
comfortable with. I put the piece in the tumbler with steel shot.
After 20+ hours there were still little white spots here and there
and white ghosts around detailed areas. I finally took it out and
used a buff and some rouge to finish polishing it. I may have
removed some of the fine silver but I had no fire scale when I
started depletion silvering so I guess it is okay, although the
finish is not as nice as it was before I started the process as I had
polished it nicely first.

Here’s the question: What is the best way to finish after the fine
silver layer is raised? I usually have small recesses and tight areas
that the steel shot can’t reach completely.

J. S. (Sue) Ellington
http://www.jsellington.com


#13
Buffing and polishing would be done after raising the fine silver. 

In the interest of balance and possibly confusion, I would argue
that buffing should be done before raising the fine silver, to avoid
buffing off the fine silver layer. A light polishing afterwards is
then all that is needed.

Noel


#14
What is the best way to finish after the fine silver layer is
raised? I usually have small recesses and tight areas that the
steel shot can't reach completely. 

After pickling, you could just wire-brush the piece to get into the
crevices, then tumble if you want, but personally I don’t tumble
anything that’s been depletion-gilded.


#15
you're going to get firestain regardless of whether you overheat or
not. The difference is that when the metal is properly depleted,
the firestain lies underneath the layer of pure metal and isn't
visible. When done improperly, with overheating, the firestain will
resurface and become visible again. 

Well, Beth, maybe one of our micro-metalurgy-minded members (say
that 5 times fast!) can intervene here. What I posted, and believe
to be true, is that if you do not heat very high on silver, you get
(pink) cuprous oxide, which pickles off, leaving fine silver over
sterling. If you heat higher (overheat, in my way of thinking) you
get (puplish-gray) cupric oxide which does not dissolve away in
pickle.

In my experience, you can get the fine silver to cover this layer,
but as you say, it is still there and it is possible to break
through to it.

The main issue here is, am I right that with more gentle heating,
the oxide that is produced is actually removed by the pickle, or am
I wrong and it is always still there under the fine silver surface?
Inquiring minds want to know!

Noel


#16

Hi Sue,

I usually have small recesses and tight areas that the steel shot
can't reach completely. 

You didn’t say what shapes of steel shot you were using.

I’d suggest you give the assorted shape mixture of shot a try. You
may even want to mix in some of the long skinny stuff used in the
magnetic tumblers if you have vary narrow spaces. The assorted
shapes seem to get into all kinds of nooks & crannies.

Dave


#17

Hi Neil,

I can’t answer all your questions, but I can help with some.

How thick is the fine silver layer assuming its done ten times as
mentioned? ie: how much repolishing will it take? 

First, I repeat the process more like 4-5 times. I don’t think I’ve
ever gone to ten or needed to!

Secondly, I don’t know how thick the fine silver/gold layer is,
because I have no way of measuring it. However, if you try the heat
patination/patterning technique I described in a post yesterday,
you’ll find that it takes some effort to remove the surface layers to
get down to the sterling; it requires more than a little sanding. If
you don’t get down to the sterling, you’ll get gray instead of black
when you do the final depletion.

As for the re-polishing… I don’t. I use a brass bristle brush on
the flex shaft. If you want a mirror finish, you’ll have to start
with one (before the depletion process) and then buff lightly and
quickly at the end. Again, the key is experimentation.

Do you quench in pickle or air cool first? 

Quench in pickle while hot (but not red hot) for the most
efficient result. If you air cool first, it will just take longer.

How does gilding compare in a practical sense to silver-plating?
It seems to me gilding would take maybe half an hour?, whereas
plating about five minutes. Is there a superior finish with the
gilding? 

No, but… You need special equipment and chemicals to plate. Also,
to prevent plated sterling from showing firestain/tarnish in time,
you should nickel plate first, before plating with fine silver (or
rhodium, or whatever).

I think someone mentioned scrubbing with a brass brush, would that
not discolor the silver? How about a nickel or stainless steel
brush?(which I used in my silversmithing days to good result) 

If you’re talking about the brushing that’s done between the
depletion repetitions, then it doesn’t seem to matter. For the final
finish, however, I was told to use nickel on silver and brass on gold
though I could never see the difference when I occasionally slipped
up and used brass on silver. I don’t believe you’re brushing enough
to make a difference, but it may just be that my eyes aren’t as
sensitive as others’.

I will look for a suitable chunk of scrap to experiment with,
might be fun. 

That’s the key! Hope you had fun :-).

Beth


#18

I am not sure what the surface qualities of a piece can or should be
after raising the fine silver. I start with a high shine and then do
the depletion process. I am reluctant to brush with a brass brush
because it scratches the surface. Maybe the idea is a consistently
frosted look? Is it possible to get a highly reflective surface or is
a matte surface the necessary outcome?

J. S. (Sue) Ellington
http://www.jsellington.com


#19

Sue,

I’ve been doing a lot with depletion gilding lately and I always use
a brass brush. Rather than scratch the surface I find that it gives
it a high shine after several depletions. Do you use soap with the
brush ? If I want a matte surface I use 4/0 steel wool for the final
finish, otherwise I do my normal silver finishing, being careful not
to abrade the surface too much and remove the fine silver.

Brian Corll
Brian Corll, Inc.
1002 East Simpson Street
Mechanicsburg, PA 17055


#20
I am reluctant to brush with a brass brush because it scratches
the surface. Maybe the idea is a consistently frosted look? Is it
possible to get a highly reflective surface or is a matte surface
the necessary outcome? 

First, a really soft brass brush doesn’t really scratch the surface,
it burnishes it. Second, no it isn’t the necessary outcome.
Personally, I don’t bother with the brass brush except for
reticulation preparation, and then I do it wet with dish soap to
lubricate. To “bring up the fine silver”, I polish first to whatever
level I wish to have on the finished piece, heat-and-pickle as many
times as needed (until no discoloration occurs any more, even on the
back or solder seams) then lightly buff to bring the shine back.
Tumbling could be a good choice too.

Noel